'customarily-kept' originates from the English word 'customary,' which comes from the Latin word 'consuetudinarius,' where 'consuetudo' meant 'custom.'

'customarily-kept' evolved from the combination of 'customarily' and 'kept,' reflecting the idea of maintaining something according to tradition.

Initially, it meant 'maintained according to custom,' and this meaning has largely remained the same in modern usage.